This application claims the priority of German Patent Document No. 101 38 083.6, filed Aug. 3, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a closed loop radiator water system for an internal combustion engine.
Usually a closed loop cooling water system is used for cooling an internal combustion engine. Critical in this respect is the possibility of forming vapor bubbles or cavitation, thus resulting in damages to the units and the lines.
From the prior art, for example DE 1 882 762, it is known to prevent cavitation by increasing the pressure level on the suction side of the cooling water pump. To this end, there is a connecting line from a compensating tank, filled with cooling water, to the suction side of the cooling water pump. The compensating tank also has air, which is fed through ventilation lines from the heat exchangers to the compensating tank. The air pressure has an impact on the pressure level in the compensating tank and, thus, on the pressure increase on the suction side of the cooling water pump. Thus, in this closed loop cooling water system, the temperature of the cooling water determines the pressure increase by the change in volume of the air. The problem is that the pressure does not begin to increase after the start of the internal combustion engine until the temperature of the radiator water increases.
In this respect the invention is based on the problem of designing a closed loop cooling water system, wherein the pressure rises faster.
The problem is solved with the invention as described hereinafter.
The invention provides that the pressure level in the compensating tank can be preset by a compressor. The compressor can be designed as a separate unit or as a component of an exhaust gas turbocharger. The use of a compressor has the advantage of a higher degree of freedom in the control of pressure increase on the suction side of the cooling water pump. Thus, it is easier to match the pressure increase to the operating point of the internal combustion engine. Thus, for example, immediately after the starting operation, the pressure level on the suction side of the cooling water pump can be raised to a safe operating value.
Between the compressor and the compensating tank there is a pressure control line, in which a pressure control valve and a non-return valve are disposed. In an embodiment of the invention, the pressure control valve can be designed as a simple spring-loaded valve. In another embodiment of the invention the pressure control valve can be designed as an electromagnetic valve, whose position is determined by an electronic control unit.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.